Store manager L.P. Cyburt boards up the windows of the business as Hurricane Sandy approaches in Ocean City, Md., on Saturday. / Jose Luis Magana, AP

by Carolyn Pesce, USA TODAY

by Carolyn Pesce, USA TODAY

Hurricane Sandy gained strength Monday as it moved north along the Eastern Seaboard, forcing the shutdown of mass transit, schools and financial markets, sending coastal residents fleeing, and threatening a dangerous mix of high winds, soaking rain and a surging wall of water up to 11 feet tall.

The monster storm's impact on some 50 million residents was fueling both apprehension and urgency.

As of 11:00 a.m. ET, maximum sustained winds were measured at 90 mph, which is a strong Category 1 storm, according to the National Hurricane Center. Wind gusts were reported as high as 115 mph.

Sandy was finally making the long-promised and unusual turn to the northwest toward the mid-Atlantic, as predicted by weather models almost a week ago. The center of the storm is forecast to make landfall along the New Jersey coast late Monday night or very early Tuesday morning.

Sandy remains a massive storm as tropical-storm-force winds of at least 39-73 mph are being felt all the way from southern Maine to the Outer Banks of North Carolina.

The storm is on a collision course with two other weather systems that would create a superstorm with the potential for havoc over 800 miles from the East Coast to the Great Lakes. About 2 to 3 feet of snow were forecast for mountainous parts of West Virginia.

The worst of the storm surge could be in the northern part of New Jersey and in New York City and on Long Island. Higher tides brought by a full moon compounded the threat to the metropolitan area of about 20 million people.

"This is the worst-case scenario," said Louis Uccellini, environmental prediction chief for the National Oceanic and Atmospheric Administration.

New York Gov. Andrew Cuomo announced 2 p.m. shutdowns of the Holland Tunnel that links lower Manhattan to New Jersey and the Hugh L. Carey Brooklyn Battery Tunnel that links Manhattan and Brooklyn. Cuomo said he made the decision because both tunnels are prone to flooding during heavy storms.

The New York City storm surge from Hurricane Sandy is already at the level of the surge during Hurricane Irene last year, even though Sandy is still hundreds of miles away, Cuomo said.

"The worst is still coming," he said during a morning news conference at which he urged New Yorkers to stay home and away from highways and the coastline. "You do not need to be going to the beach to take pictures."

Reginaldo Machado, 38, of Mamaroneck, N.Y., in Westchester County was at

Harbor Island Park taking photographs of the flooding that was swallowing park benches at about 10:15 a.m. He said he plans to stay home with his wife

and two daughters.

"I'm a little bit scared," he said.

Early Monday the Coast Guard rescued 14 of at least 16 people aboard a vessel approximately 90 miles southeast of Hatteras N.C. Two people remain missing. The replica of the tall ship made famous in the film "Mutiny on the Bounty" eventually sunk, officials said. Survivors managed to get on two lifeboats.

Sandy's storm had already surge pushed tides over seven feet in New York City Monday shortly before the arrival of the morning's high tide, the National Weather Service said. The surge added roughly three feet to the high tide, which was already higher than normal as a result of the full moon, said meteorologist Jeff Tongue.

"We think the peak of the surge will be as Sandy comes ashore tonight," with a roughly six-foot surge added to the nighttime high tide, he said.

"It's a once in a lifetime storm," Tongue said. "I've been doing this for 30 years, and I've never seen anything like this."

The storm is expected to bring 50 to 75 mph winds, up to 10 inches of rain and potential snowfall of up to two feet over 14 states beginning late Monday afternoon or early evening.

Craig Fugate, administrator for the federal Emergency Management Agency, said Monday the agency has stationed teams from North Carolina to Maine and in states as far inland as West Virginia.

"We've been moving generators, basic supplies, we would need after the storm," he said.

Fugate said he was worried about people evacuating ahead of storm surges.

First there will be the coastal impact, then the wind knocking out power and then heavy rain and flash flooding, he said, adding "we don't want people to think it's not that bad when it comes ashore."

Predicted storm surges of up to 11 feet prompted mandatory weekend evacuations in low-lying parts of New York, New Jersey, Maryland and Delaware. High-wind watches and flood warnings are in effect for all the Mid-Atlantic states and southern New England, where Sandy was expected to barrel through Wednesday.

The New York Stock Exchange reversed course and dropped its plan to have electronic trading Monday as Hurricane Sandy churned closer to New York City. Exchange officials also said the market might also close on Tuesday.

"We support the consensus of the markets and the regulatory community that the dangerous conditions developing as a result of Hurricane Sandy will make it extremely difficult to ensure the safety of our people and communities, and safety must be our first priority" the stock exchange said in a formal announcement. "We will work with the industry to determine the next steps in restoring trading as soon as the situation permits."

A number of major U.S. companies postponed quarterly earnings reports.

At least 9,000 airline flights had been canceled by Monday because of the storm, according to the FlightAware flight-tracking service. That number -- 8,962 as of 9 a.m. ET -- appears certain to grow over the next 24 hours as Sandy moves onshore.

Once Tuesday's cancellation tally is included, it's possible the total could soar over 10,000 and possibly approach the 14,000 Hurricane Irene-related flight cancellations that were reported over a four-day period in August 2011.

Two cold fronts to the west and north were on a collision course with Sandy, threatening to turn the massive storm system into a nor'easter, ushering in freezing temperatures in some regions and blanketing areas of West Virginia and other states with knee-deep snow.

President Obama and Gov. Mitt Romney canceled any election stops. Obama flew back to Washington from Florida to monitor the storm.

New York Mayor Michael Bloomberg ordered evacuations for an estimated 375,000 people in some low lying areas starting Sunday at 7 p.m. New York Gov. Andrew Cuomo ordered the city's transit service to suspend bus, subway and commuter rail service. The city's mass transit system is the nation's largest - the subway alone has a daily ridership of more than 5 million.

Obama warned residents of the region to the storm "very seriously." His visit to FEMA included a conference call with governors and mayors of vulnerable states and cities. "Anything they need, we will be there," Obama said. "And we're going to cut through red tape."

Governors from North Carolina to Connecticut declared states of emergency.

- In Virginia, where several colleges and school districts canceled classes through Tuesday, Gov. Bob McDonnell authorized up to 750 National Guard members to assist with the storm. In Delaware, Gov. Jack Markell ordered mandatory evacuations for an estimated 50,000 residents of coastal communities. Collin O'Mara, secretary of the Department of Natural Resources and Environmental Control, said Sandy could unleash record waves and tidal flooding along the coast."The potential on this is greater than the defenses that we have in most places," O'Mara said.

- New Jersey Gov. Chris Christie declared a state of emergency and ordered Atlantic City casinos evacuated - just the fourth time the city's 12 casinos had been shut since legalized gambling began 34 years ago. Christie warned state residents to be prepared for several days without electricity.

- Connecticut Gov. Dannel Malloy warned that storm surges could be the worst the state has seen in almost 75 years and urged residents along the shorelines of several cities and towns to heed evacuation orders.

Most airlines planned to cancel all flights into and out of the three major New York City area airports Sunday night and not resume service until Tuesday. Most carriers were also suspending all flights into and out of Philadelphia as well as Washington D.C's Reagan National and Dulles International airports Sunday evening. Amtrak was canceling train service to parts of the East Coast, including between Washington, D.C., and New York.

The storm's landfall along the Mid-Atlantic coast "would likely be a billion-dollar disaster," Weather Underground meteorologist Jeff Masters said. He also noted that the full moon will occur Monday, which means astronomical tides will be at their peak for the month, increasing potential storm surge flooding.

With just a few days left in what's shaped up as a tight election, Sandy was forcing Obama and Republican presidential candidate Mitt Romney to adjust campaign plans. In battleground states where the hurricane is likely to collide with a cold front to form a freak hybrid storm, Sandy "will throw havoc into the race, said Virginia Sen. Mark Warner.

Obama canceled campaign stops Monday in Virginia and Tuesday in Colorado to monitor the storm but planned to go forward with other events Monday in Florida and Ohio. Romney canceled three scheduled Sunday stops in Virginia on Sunday, opting instead to campaign in Ohio before heading Monday to Wisconsin.

Vexing both candidates: bad weather that could hinder early voting. efforts throughout the East Coast. "Obviously, we want unfettered access the polls, because we think the more people that come out, the better we're going to do," said Obama adviser David Axelrod. "To the extent that it makes it harder, that's a source of concern."

Meanwhile, the American Red Cross was readying shelters, volunteers and supplies to help coastal areas from Virginia to New England. "We want to make sure we're ready to spring into action as soon as we're needed," spokeswoman Anne Marie Borrego says.

FEMA also sent liaison officers to emergency-operations centers in Maryland, Virginia, Washington, D.C., Pennsylvania, New York and New Jersey.

The Defense Department has sent officers to deploy with the FEMA teams to coordinate possible search-and-rescue missions.

Storm surge remains one of the biggest threats from the storm: Data from CoreLogic show that more than 261,000 homes are at risk.

"This will be a long-lasting event, with two to three days of impact," says James Franklin, branch chief of the National Hurricane Center. "Wind damage, widespread power outages, inland flooding and storm surge are all likely."